1. Field of the Invention
This invention relates to an electrical cutout which is electrically connected in series between a line terminal and a load terminal. More specifically, this invention relates to an electrical cutout which includes a linkbreak lever for breaking the fuse link and interrupting the load current prior to disengaging the fuse tube or the like.
2. Information Disclosure Statement
In order to protect transformer equipment and the like in a power supply circuit, it is customary to install an electrical cutout device between the transformer line and the load. These electrical cutouts include a fusible link and removable fuseholder which cooperate automatically with each other to which break the circuit in the event of an electrical overload. Furthermore, such electrical cutouts enable a lineman to manually break the circuit between the transformer and the load.
A typical electrical cutout includes an elongated insulator of porcelain or other ceramic material. The insulator includes an insulator support disposed midway between the ends of the insulator. Usually, the insulator support is embedded within the insulator using an organic or inorganic cement for bonding the insulator support within the insulator. However, the insulator support may be secured to the mid portion of the insulator by means of metal bands or the like. The insulator support is anchored to a line pole or the like and a first and a second electrical conductor are rigidly secured to the first and second ends respectively of the insulator. The line wire from the transformer is connected to the line terminal of the first conductor and the load wire is connected to the load terminal of the second conductor. A removable fuse tube extends between the first and the second conductors and a fuse link having a first and a second end thereof extends through the fuse tube. A fusible head portion of the fuse link is secured between a first end of the fuse tube and a screw fitting cap which cooperates with the first end of the fuse tube. The second end or pigtail of the fuse link extends from the second or lower end of the fuse tube and is anchored in electrical contact with the second electrical conductor. The lower or second end of the fuse tube is pivotally connected to the lower or second conductor and the linesman by means of an insulating line pole pivots the first end of the fuse tube upwardly until the cap abuts against the first conductor and forms an electrical connection therewith. In the prior art, such electrical cutouts usually incorporate a positive latching mechanism for latching the cap into engagement with the upper or first conductor. Various proposals have been disclosed which include linkbreak levers of various configurations for breaking the fuse link prior to releasing the positive latching mechanism. In use of the prior art cutouts when an overload occurs the fuse link melts thereby breaking the electrical circuit. The fuse tubes are usually fabricated from materials which on exposure to the high temperatures generated during the melting of the fuse link generate arc extinguishing gases which escape from the interior of the fuse tube through the lower end thereof. However, when the cutout is on load and for some reason it becomes necessary to disconnect the electrical load from the supply, it will be evident to those skilled in the art that if the cap is moved out of engagement with the upper conductor in order to break the electrical circuit, arcing will occur between the upper conductor and the cap which may result in damage to the upper conductor necessitating replacement of the entire cutout. In addition, this arc creates a safety concern for the lineman who is manually disconnecting the load from the supply.
In order to overcome these problems, as stated hereinbefore, various linkbreak devices have been disclosed for breaking the fuse link within the fuse tube prior to removal of the cap from engagement with the upper conductor. In the prior art, various linkbreak levers have been proposed in which the lever extends in the plane of the insulator and fuse tube such that downward movement of the lever by the lineman using an insulating line pole results in breaking of the fuse link by means of the increased tension applied to the pigtail along the length of the fuse link. Due to the moment imparted to the fuse tube by such downward pivoting of the linkbreak lever, such prior art cutouts have necessitated the use of a positive latching mechanism as stated hereinbefore for positively latching the cap into engagement with the upper conductor. Such positive latching mechanisms have involved increased overall costs in the production of such cutouts and there has existed in the art a need of a cutout in which the frictional force between the cap and upper conductor is sufficient to hold the fuse tube in position until the fuse link is broken.
However, with conventional caps, the portion of the cap which cooperates with a detent in the upper conductor is of semispherical configuration for cooperating with the spherical detent in the upper contact. The semispherical configuration of the cap does not provide sufficient frictional resistance to prevent movement of the cap away from the detent during pivotal movement of the linkbreak lever away from the fuse tube in a plane extending through the end of the insulator and the fuse tube.
In an attempt to overcome the aforementioned problem, various proposals have been disclosed wherein the handle of the linkbreak lever extends in the aforementioned plane but is pivoted upwardly towards the fuse tube in order to avoid the disengagement of the cap from the detent. However, this disposition of the linkbreak handle is relatively difficult to operate.
Furthermore, a linkbreak lever has been proposed in which the handle of the lever extends laterally relative to the aforementioned plane and this proposal while permitting the utilization of a conventional detent arrangement has proved relatively difficult to operate with a line pole because of the lateral disposition of the handle and the increasing cost of manufacture.
U.S. Pat. No. 2,514,163 to Pitman discloses a linkbreak handle which is pushed upwardly by the lineman's line pole to break the fuse link. The upward force on the handle urges the cap against the detent of the upper conductor.
U.S. Pat. No. 2,630,508 to Meisenheimer, et al. teaches a linkbreak lever handle which extends from the pivotal point 38 in a direction from the fuse tube towards the insulator, thereby disposing the handle 39 in an inaccessible location.
The present invention seeks to overcome the aforementioned inadequacies of the prior art devices by the provision of a cap having a frustoconical configuration which increases the frictional force between the cap and the detent to prevent disengagement of the cap during a linkbreak operation.
Therefore, it is a primary object of this invention to provide an electrical cutout that overcomes the inadequacies of the prior art devices and provided an improvement which significantly contributes to the low cost of manufacture of a cutout.
Another object of the present invention is the provision of an electrical cutout in which downward movement on the handle of the linkbreak lever away from the fuse tube in a direction from the insulator towards the fuse tube results in breaking of the fuse link before disengagement of the cap relative to the detent.
Another object of the present invention is the provision of an electrical cutout having a cantilever contact which defines a detent, the detent cooperating with a cap of frustoconical configuration which provides improved retentional engagement between the cap and the detent.
Another object of the present invention is the provision of an electrical cutout which avoids the necessity of providing a positive latch between the cap and the upper contact.
Another object of the present invention is the provision of an electrical cutout in which the linkbreak lever extends away from the fuse tube in a direction from the insulator towards the fuse tube.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the invention. Particularly with regard to the use of the invention disclosed herein, this should not be construed as being limited to electrical cutouts having a single insulator but should include cutouts in which the upper and the lower conductors are respectively supported by individual insulators or the like.